"Control Break" is a term often used to denote the action in a report where, when the value in a Field changes in a particular manner, a pertinent total or subtotal can be made to appear.
This Collection demonstrates how to embed subtotals and totals in a list, as well as how to put a total at the end of a list. The example shows an alphabetical list of customers (and how much each one owes), sorted by city and state. Control breaks and subtotals occur any time the city or state changes. There is a grand total at the bottom of the list.
There are a few other example files on hand. This link takes you to the Files directory where you can download them.
If you have an example you'd like to submit, upload it, then send me a note so i can review it.